Future DrellYan program of the COMPASS collaboration Oleg

Future Drell-Yan program of the COMPASS collaboration Oleg Denisov CERN and INFN sez. di Torino 06. 01. 2010 09/11/2020 Oleg Denisov 1

Outline • Drell-Yan – physics case – – – Drell-Yan kinematics Unpolarised Drell-Yan Single (Transverse) polarised Drell-Yan Double polarised Drell-Yan J/Psi production and J/Psi <-> DY duality Access to GPDs? • Some indications to the future Drell-Yan experiments • Drell-Yan @ COMPASS: – What we are going to do – How we are going to do it • Conclusions 09/11/2020 Oleg Denisov 2

Drell-Yan Kinematics (collinear case) 09/11/2020 Oleg Denisov 3

Drell-Yan Kinematics (transverse motion) 09/11/2020 Oleg Denisov 4

Unpolarised Drell-Yan angular distributions (Collins-Soper frame) 09/11/2020 Oleg Denisov 5

Unpolarised Drell-Yan angular distributions: Lam-Tung sum rule violation 09/11/2020 Oleg Denisov 6

Unpolarised Drell-Yan angular distributions: Boer-Mulders function (cos(2ϕ) modulations) DY mechanism is sensitive to k. T -induced effects 09/11/2020 Oleg Denisov 7

Drell-Yan cross section (general form) Recent paper by Arnold, Metz and Schlegel ar. Xiv: 0809. 2262 – For the first time the general expression for the DY cross-section is derived 09/11/2020 Oleg Denisov 8

DY cross-section: Leading order QCD parton model At LO the general expression of the DY cross-section simplifies to: Thus the measurement of 5 asymmetries (modulations in the DY cross-section): 09/11/2020 Oleg Denisov 9

Single polarised Drell-Yan: SSA N. B. : ϕS 1 angle in D. Boer, Phys. Rev. D 60, 014012 is not exactly equivalent to ϕS used by us so far (Arnold, Metz and Schlegel ar. Xiv: 0809. 2262) but similar 09/11/2020 Oleg Denisov 10

TMD PDF effect SIDIS <->DY A. Schafer – Mainz’ 09 J. C. Collins, Phys. Lett. B 536 (2002) 43 J. Collins, talk at LIGHT CONE 2008 11

Double polarised Drell-Yan: direct access to Transversity M. Nekipelov -> PAX Feasibility study is underway, polarised antiprotons(>20%) - not a trivial issue 09/11/2020 Oleg Denisov 12

J/ – Drell-Yan duality • • • J/ – DY duality close analogy between Drell-Yan and J/ production mechanism: – Occurs when the gluon-gluon fusion mechanism of the J/ production is dominated by the quark-quark fusion mechanism – We can expect that the duality is valid in the COMPASS kinematic range Key issue for the applicability of the J/ signal for the study of hadron spin structure J/ production mechanism by itself is an important issue J/ substitution 09/11/2020 Oleg Denisov 13

Drell-Yan processes and access to GPDs Very preliminary – feasibility is under discussion now, some indications: • O. Teryaev: Drell-Yan pair production in the pion-nucleon collisions for large x. F (the region whose exploration is favourable in COMPASS kinematics) is sensitive to such an important and hot ingredient of pion structure as its light-cone distribution (DA). In other words in this kinematic range pion participate in the interaction coherently (as pion) rather then by only one of its quark. References: A. P. Bakulev, S. V. Mikhailov and N. G. Stefanis, Phys. Lett. B 508, 279 (2001) A. Brandenburg, S. J. Brodsky, V. V. Khoze and D. Mueller, Phys. Rev. Lett. 73, 939 (1994) A. Brandenburg, D. Mueller and O. V. Teryaev, Phys. Rev. D 53, 6180 (1996) • B. Pire, O. Teryaev: Semiexclusive DY – crucial test of the GPDs universality (time-like process contrary to the Deep Inelastic scattering) Reference: B. Pire, L. Szymanowski, ar. Xiv: 0905. 1258 v 1 [hep-ph] 8 May 2009 09/11/2020 Oleg Denisov 14

Some indications for the future Drell-Yan experiments TMD PDFs – ALL are sizable in the valence quark region Sivers effect in Drell-Yan processes. 
M. Anselmino, M. Boglione U. D'Alesio, S. Melis, F. Murgia, A. Prokudin 
Published in Phys. Rev. D 79: 054010, 2009 09/11/2020 Oleg Denisov 15

Some indications for the future Drell-Yan experiments Safe region: 4. < M < 9. Gev/c 2 09/11/2020 Oleg Denisov 16

Some indications for the future Drell-Yan experiments 1. Drell-Yan experiments: – High luminosity (DY Cross Section is a fractions of nanobarns) and large angular acceptance, better pion or antiproton beams (valence anti-quark) – Sufficiently high energy to access ‘safe’ of background free Mll range ( 4 Ge. V/c < Mll < 9 Ge. V/c) – Good acceptance in the valence quark range x. B > 0. 05 and kinematic range: τ = x. Ax. B = M 2/s > 0. 1 2. Polarised Drell-Yan: – Good factor of merit (Fo. M), which can be represented as a product of the luminosity, target polarisation (dilution factor f) and beam polarisation Pbeam (if any): Fo. M ~ L × f 2× P 2 beam 09/11/2020 Oleg Denisov 17

Future Drell-Yan experiment • Fixed target experiments (COMPASS, E 906, J-Park) characterised by: – Very high luminosity (>1033 cm-2 s-1) – Only muon in the final state (hadron absorber has to be used because of the ‘all forward’ geometry and high luminosity) – Light unpolarised targets (liquid hydrogen and deuterium) and solid state polirased targets (NH 3, 6 LD) – Pion, proton and (probably) antiproton (COMPASS) beams • Collider experiments (RHIC, NICA SPD, PAX) – Moderate luminosity – High universality (not only TMD PDFs, J/Psi and related aspect but also formfactors, various hard processes – not a topic of this talk) 09/11/2020 Oleg Denisov 18

COMPASS experiment at CERN COMPASS NH 3 or 6 Li. D solid polarised target 09/11/2020 Oleg Denisov 19

Why Drell-Yan @ COMPASS 1. Large angular acceptance spectrometer 2. SPS M 2 secondary beams with the intensity up to 6 x 107 particles per second 3. Large acceptance COMPASS Superconducting Solenoid Magnet 4. Solid state polarized target working in frozen spin mode with long relaxation time; 5. a detection system designed to stand relatively high particle fluxes; 6. a Data Acquisition System (DAQ) that can handle large amounts of data at large trigger rates; 7. The dedicated muon trigger system For the moment we consider two step DY program: • The program with high intensity pion beam • The program with Radio Frequency separated antiproton beam 09/11/2020 Oleg Denisov 20

DY cross section and acceptance @ COMPASS 09/11/2020 Oleg Denisov 21

DY acceptance @ COMPASS Sivers Function prediction (M. Anselmino et al) COMPASS Acceptance Prediction for Sivers function as a function of x, COMPASS acceptance in xp and acceptance coverage xπ. vs. xp 09/11/2020 Oleg Denisov 22

Access to the TMD PDFs @ COMPASS 09/11/2020 Oleg Denisov 23

DY Feasibility@COMPASS Beam Test 2007 (no hadron absorber) 09/11/2020 Oleg Denisov 24

Pt range covered by COMPASS Pt coverage (Pt ~ 1 Ge. V what makes COMPASS sensitive to the contribution from the TMD PDFs but not from higher twists – see slide 4) Previous experiments: 09/11/2020 Oleg Denisov 25

DY Feasibility@COMPASS Beam Test 2009 (with hadron absorber I) 09/11/2020 Oleg Denisov 26

DY Feasibility@COMPASS Beam Test 2009 (with hadron absorber II) 09/11/2020 Oleg Denisov 27

DY Feasibility@COMPASS Beam Test 2009 (with hadron absorber III) 09/11/2020 Oleg Denisov 28

Some results of 2009 DY beam test: radio-protection issues and tracking detectors occupancies • • RP - the detected radiation level is factor 6 lower than allowed one (3 u. Sv), in a good agreement with simulations done by COMPASS and CERN RP (pion beam intensity ~8 x 10^7 pions per spill (10 seconds)) The tracking detectors occupancy downstream of hadron absorber is factor 10 lower compare to the normal muon running conditions 09/11/2020 Oleg Denisov 29

Sivers and expected statistical error @ COMPASS 09/11/2020 Oleg Denisov 30

COMPASS: Summary • • • Pion and, later, antiproton beams (50 -200 Ge. V), Drell-Yan process dominated by the contribution from the valence quarks (both beam and target), τ = x 1 x 2 = Q 2/s ≅ 0. 05÷ 0. 3 Solid state polarised targets, NH 3 and 6 Li. D, in case of hydrogen target – pure u-dominance Statistical error on single spin asymmetries is on the level 1÷ 2% in two years of data taking Lo. I already submitted to CERN SPSC (January 2009) Proposal will be submitted to the SPSC at the beginning of 2010 First Drell-Yan data taking >2012 09/11/2020 Oleg Denisov 31

Conclusions • Next decade looks very promising for the new Drell-Yan experiments – a lot of activity in the field • The new generation of the polarised Drell-Yan programs will contribute in decisive way into our understanding of the hadron structure • Access to the valence quarks contributions as well as high luminosity are important prerequisits to the successful Drell-Yan experiment 32

• Spares 33

WHAT ABOUT A RF SEPARATED pbar BEAM ? ? ? First and very preliminary thoughts, guided by • recent studies for P 326 • CKM studies by J. Doornbos/TRIUMF, e. g. http: //trshare. triumf. ca/~trjd/rfbeam. ps. gz E. g. a system with two cavities: RF 1 L RF 2 DUMP Momentum selection Choose e. g. DFpp DF = 2 p (L f / c) (b 1 -1 – b 2 -1) with b 1 -1 – b 2 -1 = (m 12 -m 22)/2 p 2 L. Gatignon, 17 -10 -2006 Preliminary rate estimates for RF separated antiproton beams 34